Self-propelled rotary mower

ABSTRACT

A rotary mowing or cutting unit is suspended beneath the central portion of a jeep-style traction vehicle which has a low center of gravity and is capable of speeds up to 14 miles per hour. Three cutting blades are arranged within a mower deck for cutting slightly overlapping swaths in the direction of travel of the vehicle, and combining to cut an overall swath which is greater than the vehicle width. The mowing unit is provided with side runners which extend forward of the deck and rear rollers for engaging ground obstructions and limiting downward movement of the mower unit. The deck is mounted to the vehicle by a mechanism which permits an operator to adjust the height of the cutter blades while allowing the unit to be raised should it encounter an elevation in the ground. The mounting mechanism prevents the cutter unit from tilting fore and aft while allowing one side of the unit to lift if the runner on that side engages a ground elevation. A spring-biased counterbalancing system offsets most of the weight of the mowing unit to permit a fast vertical reaction at high ground speeds. The mowing unit is designed to cut the volume required at these speeds while separating out debris struck by the blades.

United States Patent Aug.3l, 1971 [54] Q SELFJROPELLED ROTAR Y MOWER 8Claims, 5 Drawing Figs.

[52] U.S. Cl. 56/13.7, 56/6, 56/14.9 [51] Int. Cl. i A6111 35/26 [50]Field of Search 56/25.4, 6, 295; 280/53 FE [56] References Cited UNITEDSTATES PATENTS 3,063,226 11/1962 Pfauser 56/25.4 3,433,003 3/1969Musgrove... 56/26 3,512,344 5/1970 Kortum 56/25.4 1,482,880 2/1924Barton..... 180/53 FE 2,801,510 8/1957 Colburn 56/25.4 2,862,343 12/1958Wood 56/25.4 2,901,257 8/1959 Teagle.. 56/25.4 X 2,940,241 6/1960 Stahl.56/25.4 3,077,065 2/1963 Samways et al. .56/25.4 3,136,106 6/1964Joslin 56/25.4

1/1964 Colburn 6/1966 Colburn Primary Examiner-Louis G. ManceneABSTRACT: A rotary mowing or cutting unit is suspended beneath thecentral portion of a jeep-style traction vehicle which has a low centerof gravity and is capable of speeds up to 14 miles per hour. Threecutting blades are arranged within a mower deck for cutting slightlyoverlapping swaths in the direction of travel of the vehicle, andcombining to cut an overall swath which is greater than the vehiclewidth. The mowing unit is provided with side runners which extendforward'of the deck and rear rollers for engaging ground obstructionsand limiting downward movement of the mower unit. The deck is mounted tothe vehicle by a mechanism which permits an operator to adjust theheight of the cutter blades while allowing the unit to be raised shouldit encounter an elevation in the ground. The mounting mechanism preventsthe cutter unit from tilting fore and aft while allowing one side of theunit to lift if the runner on that side engages a ground elevation. Aspring-biased counterbalaancing system offsets most of the weight of themowing unit to permit a fast vertical reaction at high ground speeds.The mowing'unit is designed to cut the volume required at these speedswhile separating out debris struck by the blades."

PATENIED Ausal nan SHEET 1 BF 2 mw mw INVISNfI'U/if EARL ROOF PATENTEBA1183] 197! 3,601 958 SHEET & u? 2 FIG. 2

I N VENTUR. EARL ROOF SELF-PROPELLED ROTARY MOWER BACKGROUND- Thepresent invention relates to self-propelled rotary mowers; moreparticularly, it relates to a self-propelled rotary mower capable ofcutting swaths of approximately 60 inches in width and at speeds of upto 14 miles per hour.

Self-propelled rotary mowers may be classified into two general areas.One of thesetareas includes mower units which are detachably mountedbeneath a conventional farm tractor. Farm tractors have the powerrequirements capable of higher speeds, but they also have a narrow frontwheel base and a relatively high center of gravity, thus restrictingtheir maneuverability and usefulness in cutting on slopes.

The other type of rotary power motor which is selfpropelled is referredto as the garden mower; and although it has a low center of gravity andfairly wide wheel base, it lacks the power and mowing capacity capableofachieving mowing speeds any higher than 3-4 miles per hour. Further, inthe normal garden-type of self-propelled rotary mower, the frame of thevehicle is normally so low that there is no provision for a substantialadjustment of the height of the cutting blades as required to cut bothgrass and high weeds.

The present invention combines the low cost and maneuverability ofgarden mowers with the higher power and speeds of the tractor-typemowers while permitting substantial adjustment of the mowing or cuttingunit to achievecutting of both lawns and high weeds at these heretoforeunknown mowing speeds.

Thus, the present invention is capable of mowing speeds of up to 14miles per hour and although it cuts a narrower swath than the moreexpensive and much more powerful tractortype mower pulling reel orrotary cutters, it can accomplish the same cutting volume in a giventime while providing a much less expensive unit having a broader rangeof utility.

The mowing unit is suspended beneath the center portion of a jeep-typetraction vehicle which has a relatively low center of gravity and a widewheel base. Thus, the vehicle is capable of cutting on hill slopes whichwould prohibit the use of a tractor with its high center of gravity yetwhich permits the adjustment of the height of the cutter blades over asubstantial range, as desired. The mowing unit may bedetached from thetraction vehicle to permit the latters use as a general purpose utilityvehicle.

The vehicle is equipped with an 18 horsepower engine and a hydrostatictransmission; and a belt couples to engine power to drive the cutterblade at a constantspeed. The hydrostatic transmission couples theengine power to the rear drive wheels of the vehicle and permits acontinuously variable range of forward and reverse speeds for thevehicle while the cutter blades are driven at maximumspeed as determinedby the engine speed.

Three cutting blades are supported by a mowing deck and arranged in agenerally triangular pattern so that the center and lead blade cuts aswath which slightly overlaps the swaths cut by the side blades.

The mower deck is mounted beneath and centrally of the vehicle so thatit may be adjusted to variousheightsabove the ground; and it is providedwith a pair of side runners projecting forwardly of the mower deck todefine a minimum height below which the cutter blades cannot be lowered.The mounting system includes a scissors linkage mechanism on each side.of the mower deck interconnecting it with the frame of the tractionvehicle. The scissors linkages permit the raising of either side of themowing unit in a parallel line relative to the direction of travel ofthe vehicle while preventing tilting in a fore and aft direction. Acounterbalancing mechanism offsets the greater portion of the weight ofthe mowing unit; and it is connected centrally of the mower deck sothat, in combination with the side scissors links if either of the siderunnersencounters an obstruction, the mower unit. will have a fastresponse time and tilt about a line parallel to the direction of vehicletravel to lift the deck and cutters. The suspension system also includesa wishbonemounting link interconnecting the front, sloped band of themower deck with a forward crossbar of the vehicle frame to maintain theproper horizontal orientation of the mowing unit beneath the tractionvehicle when mowing flat terrain while resisting lateral movement of themower deck relative to the vehicle frame. Two flexible chain linksinterconnect the rear portion of the mower deck with a rotatable barextending transverse of the vehicle. A hand-actuatable lever isconnected to the transverse bar; and rotation of this lever raises themower deck by means of the flexible links. The side scissors links andthe wishbone link maintain the parallel orientationof the mower unitrelative to the ground so that the flexible links permit raising of themower unit while defining a predetermined height below which it will notdescend.

The vehicle is also provided with a storage section including a reardrop gate which enhances the broader utility of the vehicle; and thestorage area may be used for holding major obstructions which may get inthe way during the mowing operation. The mowing unit is adapted toprocess the greater quantity of grass or weeds encountered in the higherspeeds at which the combination is designed to operate by providing thatthe cutting blades be of the propeller type to create an updraft and byproviding a relatively large chamber between the upper surface of themower deck and the blades so that the cut material is forced by the aircurrent upwardly of the blades and processed through an open side of themower deck. Other, more solid and heavier objects such as rocks andglass, if struck, are propelled toward the downwardly inclined front andback walls of the mower deck and deflected toward the ground.

With this combination, the inventive device is able to mow grass atspeeds up to 12-14 miles per hour and weeds at speeds of up to 10 milesan hour without undue congestion of the cut material in the mowing unitand with a better flexibility and safety than is provided by tractors.At the same time, the mower unit may be set at any predetermined heightabove the ground; and yet, when the side runners encounter anobstruction, the mower unit quickly responds (due to thecounterbalancing mechanism) to tilt about a line parallel to thedirection of travel of the vehicle and ride over the obstruction. Theentire mower unit is easily detached entirely from the vehicle, whichmay then be used as a general utility vehicle or even as a golf cart.

Other features and advantages of the present invention will be apparentto persons skilled in the art from the following detailed description ofa preferred embodiment accompanied by the attached drawingwhereinidentical reference numerals will refer to like parts in the variousviews.

THE DRAWING FIG. 1 is a perspective view of a self-propelled rotarypower mower according to the presentinvention, partially in 'phantom toshow details of he mowing unit;

FIG. 2 is a front perspective view of the unit of FIG. 1 illustratingthe detachment of the mowing unit from the traction vehicle;

FIG. 3 is a plan view of the mower unit;

FIG. 4 is a vertical cross section view of a bearing mount for a cutterblade taken through thelines 4-4l of FIG. 3; and

FIG. 5 is a schematic diagram of the cutting unit in operation.

DETAILED DESCRIPTION Turning now to FIG. 1, the traction vehicle isgenerally designated by reference numeral 10; and it has fourgroundengaging wheels lll (only three of which are shown) equipped withflotation tires, and an engine generally designated 12 located beneath ahood 13. The engine 12 powers a clutch 12a coupled to a drive shaft11212 which extends in front of the engine for coupling powertoa mowingorcutter unit generally designated 14 and mounted centrally beneath thetraction unit 10. The engine 12 also powers a main drive shaft accordingto known technique which couples power to the rear drive axle through aconventional hydrostatic transmission, the speed of which is controlledby means of a joy stick 15 located between two seats 16 and 17 mountedin the vehicle 10.

The seat 17, is, of course, the operator's or drivers seat; and astorage section generally designated 18 is located behind the seats 16and 17. The storage area 18 is accessible through the opened top orthrough a drop gate 19. It will be observed that the seats 16 and 17locate the riders within the vehicle and not on the vehicle as is commonto the small garden-type mowers thereby offering greater safety fromoverhead branches and bushes. Further, the storage section 18 of thevehicle enhances its use as a general utility vehicle when the mowerunit is detached, or it may be used to transport larger objectsencountered during the mowing operation as they are removed from thepath of the vehicle.

The traction vehicle 10 has the general shape and appearance of a jeepvehicle on a reduced scale. It is not necessary that it have four-wheeldrive, although this is not excluded from the inventive concept; andpreferably, the horsepower rating of the engine 12 is of the order of 18horsepower which provides sufficient energy to drive the vehicle at arate up to 14 miles per hour while still maintaining full cuttingoperation of the suspended cutter unit. The wheel base of the vehicle is56 inches; and it has a low center of gravity in comparison withconventional farm tractors thus providing it with greatermaneuverability than a farm tractor and an ability to cut weeds or grasson a slope of greater inclination than that which a farm tractor is ableto negotiate. Either or both the seats 16 and 17 may be removed ifgreater storage area is required when the vehicle is used as a utilityvehicle.

As used herein, the term jeep-type vehicle refers to a four-wheeltraction vehicle having a front-end mounted motor and which is capableof carrying passengers within the vehicle and providing a' rear storagearea. It is characterized by having a relatively low center of gravityas compared with a farm tractor and a wide wheel base as compared withthe front wheels of a farm tractor or a conventional small garden mower.

Turning now to the mowing unit, it includes an integral housing or deckcomprising a top plate 20, first and second front plates 21 and 22 whichextend downwardly and forwardly from the top plate 20 and which areinclined relative to one another to .form a pilot for the cutterhousing, a vertical sideplate 23, and a rear section 24 which extendsdownwardly and rearwardly from the top plate 20.

Referring now to FIG. 3, the front inclined plates 21 and 22 togetherwith the sideplate 23 and the back plate 24 provide a peripheral bandhousing the cutter blades. The side opposite plate 23 (generallydesignated by reference numeral 25) is left open for exhausting the cutgrass or weeds. Three cutter blades are rotatably mounted on the topplate 20 of the deck of the mowing or cutter unit; two of the blades aredesignated 26 and 27 and shown in phantom in FIG. 1, and the right sideblade (when viewed from the standpoint of an operator seated in seat 17)is designated 28 in FIG. 4. Each of the cutter blades 26-28 is the typecommonly referred to as a propeller type of cutter blade in that thecutting portions have a slight draft proceeding from the cutting edge tothe trailing edge of the blade to create a vertical air current to raisethe grass for cutting and to lift the cut material above the cuttingblades.

All three cutter blade mountings are similar, and only one need bedescribed in greater detail. Referring then to FIG. 4, which illustratesthe mounting for the blade 28, a central shaft 30 extends through thetop plate 20 and receives a pulley 31 secured to the shaft above the topplate 20. Plates 32 and 33 are mounted on either side of the top plate20 of the deck; and the shaft 30 extends through them. The plate 33 isprovided with the center bearing 34 which supports the shaft 30; and theplates 32 and 33 as well as a housing 35 of inverted conical shape andextending coaxially with the shaft 30, are secured to the top plate 20by means of bolts 36. The bolts 36 are received in slots 32a in plate 32and slots 33a in plate 33 in the case of the side cutter blades sothatthe cutter mountings may be moved back to tighten their drive belts, asdescribed presently.

The lowermost portion of the conical housing 35 is provided with asecond bearing 38 supporting the shaft 30; and the blade 28 is fastenedto the bottom of the shaft 30 outside of the conical housing 35. Thus,when the pulley 31 is driven, the blade 28 rotates. Similar bearingmounts are provided for the other cutter blades; and the distancebetween a cutter blade and the top 20 of the mower deck is about 4inches to provide an upper cavity of substantial volume which isadvantageous in handling the great volume of material at the highcutting speeds. The conical bearing housings cooperate in providing aneven upward draft to force the cut material out of the open side of themower deck, as shown schematically in FIG. 5. This is considered animportant advantage in processing the substantial quantities of cutmaterial when the vehicle is operated at high speeds.

The pulley fastened to the shaft attached to the central cutting blade27 is generally designated by reference numeral 40; and it includesthree superposed pulley channels as seen in FIG. 1. The pulley attachedto the shaft which drives the cutter blade 26 is designated 42 in FIG.3.

A first belt 43 interconnects the pulley 42 with the lowermost channelof the pulley 40. A second belt 44 interconnects the pulley 31 with theintermediate channel of the central pulley 40; and a third belt 44a (seeFIG. 1) interconnects the top channel of the pulley 40 with a pulley 45fastened tothe drive shaft of the motor 12. The belt 44a makes aright-angle turn by means of two idler pulleys 47 and 48 which arejournaled on either side of a horizontal shaft 49 which is received in asleeve 50 extending vertically upward and fitting telescopically over ashaft 51 secured to the frame of the vehicle 10. The sleeve 50 isvertically adjustable along the shaft 51 by means of a pin 54 tocompensate for stretching under normal wear, as with the adjustablemountings previously described to tighten belts 43 and 44. When themanual clutch which drives the shaft 12b is engaged, the drive belt 44ais turned by the drive shaft pulley 45, and each of the pulleys 31, 40and 42 together with their associated cutter blades is driven so thatall of the cutter blades rotate in the same direction, whichpreferablyis in' a direction so that the leading cutting edge of eachblade moves toward the direction of travel and then around toward theopening 25 on the deck of the mower unit (i.e. clockwise when viewedfrom the top). This passes the cut material out the side opening on themower deck and above the cutting blades in the direction of the arrowsin FIG. 3.

A first side runner 55 is attached to the left side of the mower deck bymeans of a first bracket 56 attached to the inclined front plate 22 ofthe mower deck and a rear bracket 57 attached to the backplate of themower deck. The runner 55 contains an upwardly and forwardly curvingportion 58 so that any object which is encountered by it will tend toraise the mower deck. A second runner 59 is similarly attached to theother side of the mower deck (see FIG. 3).

On the rear plate 24 of the mower deck, there are provided first andsecond rollers, designated respectively by reference numerals 60 and 61,rotatably received on shafts'journaled in mounting brackets 62. Therunners 55 and 59 are designed to engage ground elevations to eitherside since the mower deck extends beyond the wheel base; and the rollers60 and 61 engage ground elevations between the wheels to lift the mowerdeck.

Turning now to FIG. 2, the attachment of the cutter unit to the vehicleframe will now be explained in greater detail. As already mentioned,'itis deemed highly desirable while operating at the high speed which thepresent invention' is capable of achieving, to mount the mowing unit notonly that it may be adjusted to a predetermined height above the ground(and capable of being lifted above that height) but also so that eitherof the side runners 55 or 59 engaging a ground elevation will lift itsside of the mowing unit so that the entire cutter unit may be raised ortilted about the ground-engaging portion of the opposite runner. Thispermits a side-to-side inclination of the cutter blades relative to thehorizontal but prevents a foreto-aft inclination of the cutter bladesrelative to the horizontal.

Toward this end, first and second side scissors linkages, generallydesignated by reference numerals 65 and 66, interconnect the cutter unitwith the sides of the vehicle.

As seen in FIG. 1, the left-side linkage 65 includes an outer link 68pivotally connected to a bracket 69 attached to the front plate 22 ofthe mower deck and slidably received on a stud 70 secured to the side ofthe vehicle. The rear of the link 68 defines a slot 71 which iselongated in the direction of elongation of the link and which seatsover the stud 70 so that as the cutter unit is raised and lowered, theslot 71 will slide along thestud 70. The scissors linkage 65 alsoincludes an inner link 73, the forward end of which is pivotallyconnected at 74 to the vehicle 10.

The rear portion of the link 73 is provided with a slot 75 (similar tothe slot 71 of the link 68) which is received on a stud 76 attached to abracket 77 secured to the rear wall 24 of the mower deck. The links 68and 73 are pivotally connected by means of a pin 80 to provide theopening and closing scissors action; thus, if there is an upward forcetransmitted to the link 68 by means of the forward bracket 69, a similarupward force will be transmitted to the rear portion of the mower deckthrough the link 73, the bracket 77 and the pin 76 to raise the entireleft side of the mower deck in a horizontal line parallel to thedirection of travel of the vehicle thus tilting it about the oppositerunner.

The right side scissors linkage 66 is constructed similar to thescissors linkage 65 already described; and the two operate in a similarmanner but on complementary sides of the mower deck.

The pilot of the mower unit is connected to the forward portion of thevehicle frame by means of a wishbone link 81 which is pivotallyconnected respectively at 82 and 83 to brackets 84 and 85 attached tothe front plates 21 and 22 of the mower deck pilot. A neck portion 86 ofthe wishbone 81 is fitted through an aperture 87 in an angle bracket 88which is secured to the forward cross bar of the vehicle frame as at 90(see FIG. 1 The wishbone linkage described permits the raising andlowering of the mower unit relative to the vehicle frame whilepreventing any lateral displacement or rotation about a vertical axisthus stabilizing the same beneath the vehicle for all elevations.

Forraising and lowering the mower unit beneath the vehicle, a transverserod 92 is journaled in brackets 93 and 94 which are secured to thevehicle frame. Forwardly extending arms 95 and 96 are located towardeither side of the transverse bar 92; and a lever 97 is attached to theleft side of the transverse bar 92 and extends upwardly and slightlyforward to a position adjacent the drivers seat 17 where an outwardlyextending handle 98 is provided. On the side of the vehicle, there islocated a plate 99 having a series of apertures 100 for receiving thepin 101 extending inwardly of the lever 97. Attached to the distal endof the arm 95 is a chain 104; and a similar chain 105 is attached to thedistal end of the arm 96. The lower ends of the chains 104 and 105 areconnected to the rear plate 24 of the mower deck at the locations106 and107 indicated in FIG. 3. When the lever 97 is rotated in the clockwisedirection as viewed from the left side of the vehicle, the arms 95 and94 which are secured to the transverse bar 92 also rotatecounterclockwise thereby lifting the chains 104 and 105 which pull themower unit upward. It will be apparent that through the use of thechains 104 and 105, the setting of the crank arm 97 determines a minimumheight below which the cutter unit will not be lowered through gravity;and yet, should either of the side runners attached to the mower deckencounter a ground elevation at any cutter height, the respective runnerwill raise its side of the mower unit. it will also be apparent that anyflexible linkage of sufiicient strength, such as a wire cable, may beequally well used in place of the chains I 104 and 105. i

In order to offset the weight of the mower unit, a bell crank 110(located approximately at the center of FIG. 1) having an upwardlyprojecting portion 111 and a horizontally and forwardly projectingportion 112 is pivotally mounted by means of a pin 113 in a bracket 114secured to the vehicle frame. A spring 115 is connected under tensionbetween the upper end of the upper portion 111 of the bell crank 110 anda fixed location on the vehicle 116. Thus, the spring 115 tends torotate the bell crank 110 in a clockwise direction when viewed from theleft side of the vehicle. However, the forward end of the section 112 ofthe bell crank 110 is attached to the center of the mower deck by meansof a link which is pivotally connected at one end to the forwardportion. 112 of the bell crank 110 and pivotally connected at its lowerportion to a bracket 121 which is attached to the top plate 120 of themower deck. The force tending to rotate the bell crank 110 in aclockwise direction caused by the tension of the spring 115 is less thanthe weight of the mower deck so that the latter will lower under forceof gravity to the proper cutting height. However, the net weight of themower unit is substantially less than its actual weight so that it willreact quickly when an obstruction is encountered. Further, thiscounterbalancing system permits the easy vertical adjustment of thecutter unit by means of the hand-actuatable lever 97.

It will be appreciated that other systems including poweractuatedmechanisms may be employed to raise the cutter unit in place of thehand-actuated system showmFor example, an electric motor mounted on thevehicle frame may be coupled to the mower deck by means of a rigid shaftjoumaled in a ball bushing which permits retraction and extension of theshaft to raise and lower the cutter unit. Other equivalent mechanisminclude hydraulic and pneumatic power devices.

Referring again to FIG. 2, the entire cutter unit may be detached fromthe traction vehicle by removing the side bolts securing the upperportions of the scissors linkages 65 and 66 to the vehicle and removingthe pivotal connection of the link 120 with the forward section 112 ofthe bell crank 110. The chains 104 and 105 also must be removed from thearms 95 and 96 of the crossbar 92 to drop the cutter unit onto itsrunners 55 and 59. A slight rearward movement of the cutter unit willthen remove the neck 86 of the wishbone link 81 from its bracket 88.

Turning again to FIG. 5, there is illustrated a very important operatingand safety feature of inventive machine wherein the rotating bladesstriking a heavier object will propel it toward the inclined front orrear wallof the cutter deck. The inclination of the walls (preferablyabout 30) will force the heavier objects directly downward whileseparating the lighter cut material which is sucked by the propellerblades upwardly into the chamber above the blades and thence forced outthe discharge chute. In particular I have noticed that if a bladestrikes glass or a bottle, it will shatter upon impact but will bedeflected immediately downward when it strikes the inclined walls of thehousing.

Having thus described in detail a preferred embodiment of the inventivetraction vehicle, mowing unit and itsassociated suspension system, itwill be appreciated that the combination is advantageously designed forhigh speed operation with a vehicle having a low center of gravity andwide wheel base for high maneuverability. The cutting unit may belowered by a hand-actuated lever to any desired height above a certainminimum height of the cutting blades as defined by the ground-engagingrunners attached to the sides of the mower deck. The suspension systempermits raising of either side of the suspended mowing unit whilemaintaining the opposite side at its predetermined height; and this isdone with the raised side maintaining its parallel relation to theground. The

side scissors linkages together with the flexible links attached to themower deck advantageously accomplish this result; and they cooperatewith the front wishbone link to stabilize the mower deck in yaw.

The main power is coupled to the cutter shafts by means of a flexiblebelt which permits raising and lowering of the mowing unit without theneed for adjusting the driving mechanism. The counterbalancing mechanismpermits fast reaction of the mower deck to an encountered elevation orobstruction and further eases the burden on raising and lowering themower unit by means of the hand-operated lever. Further, the inclinationof the pilot and rear sections of the mower housing permits theseparation of solid debris from the cut material by deflecting the solidmaterial directly to the ground whereas the updraft created by therotating propeller-type blades lifts the cut material to an enlargedcavity defined between the rotating blades and the top plate of themower deck, and thence out the side opening to substantially increasethe ability of the cutter unit to process cut materials.

Persons skilled in the art will be able to devise other structures andmechanisms capable of accomplishing certain of the functions and resultsof the individual elements of the described combination withoutdeparting from the inventive principle; and it is, therefore, intendedthat such modifications and equivalents be covered as they are embracedwithin the spirit and scope of the appended claims.

1. In combination, a four-wheel traction vehicle having an engine forpowering said vehicle and characterized by having a relatively lowcenter of gravity and wide wheel base; a rotary mowing unit having acovering deck and a plurality of cutting blades mounted to said deck forrotation about a vertical axis and located beneath said deck; adjustablesuspension means for supporting said deck beneath said vehicle at apredetermined but adjustable height above the ground, said suspensionmeans permitting said mowing unit to be raised when the same encountersa ground obstacle while preventing said unit from being lowered belowsaid predetermined height and including flexible link meansinterconnecting said mower deck and said vehicle for supporting saidmowing unit; lift means carried by said vehicle and coupled to saidflexible link means for raising and lowering said mowing unit to saidpredetermined height; drive means including a belt drive system forcoupling power from said engine to drive said blades; first and secondside linkage means separately interconnecting said deck with saidvehicle for maintaining said deck in parallel relation with a lineextending inthe direction of travel of said vehicle while permittingsaid mowing unit to be tilted about said line whereby one side of saidmowing unit may be raised in parallel relation and independent of theother side; a wishbone linkage having a neck pivotally connected withthe vehicle frame and first and second base portions pivotallyinterconnecting with the deck of said mowing unit whereby said mowingunit may be raised and lowered relative to said vehicle while stabilizedagainst rotation about a vertical axis; and counterbalancing linkmechanism interconnecting said deck of said mowing unit with saidvehicle for partially offsetting the weight of said mowing unit.

2. The apparatus of claim 1 wherein said first and second side linkagemeans each comprise a scissors linkage including first and second linkspivotally interconnected with each other intermediate their ends, afirst end of said first and second links being pivotally connectedrespectively with said mower deck and said vehicle, the other ends ofsaid first and second links defining slots for receiving first andsecond pins connected respectively to said vehicle and said mower deckspaced apart from said first and second pivotal connections whereby saidslots will ride along their associated pins when said mowing unit israised and lowered relative to said vehicle while maintaining each sideof said unit parallel to a horizontal line in the direction of travel ofsaid vehicle.

3. The apparatus of claim 1 wherein said mowing unit deck defines anopen side for the passage of cut materials and the swaths of said bladesoverlapping in the direction of movement of said vehicle, said bladesdefining an upward draftfor moving out materials thereabove and intosaid enlarged cavity.

4. The apparatus of claim 3 wherein the forward end of said mower deckincludes first and second, forwardly and downwardly projecting platesextending from the top of said deck and inclined relative to each otherto define a pilot for said mowing unit, and a rearwardly and downwardlyprojecting rear plate, whereby heavy objects struck by said rotatingblades and deflected'by said pilot or rear plate of said deck will bedirected downwardly and the cut material directed upwardly of saidblades and exhausted through said side opening.

5. The apparatus of claim 4 further comprising first and secondground-engaging runners attached to the sides of said mower deckrespectively and disposed beneath the same to define a minimum heightfor the cutter blades when said runners slide along the ground.

6. The apparatus of claim 5 further comprising rear roller meanspivotally attached centrally of said rear plate of said. mower deck andextending beneath the same for engaging ground elevations occuring inthe center of said mower deck.

7. In combination, a traction vehicle having a frame and a pair of frontwheels and a pair of rear wheels; a cutter unit including a deck beneathsaid vehicle and between said front and rear wheels; scissors linkagemechanism interconnecting each side of said deck with said vehicle framefor permitting raising of either side of said cutter unit independentlyof the other while preventing tilt of said cutter unit in a fore-and-aftdirection, link means interconnecting said cutter deck and said framefor permitting raising and lowering of said deck while preventingrotation thereof relative to said frame about a vertical axis;adjustable flexible link means interconnecting said cutter deck withsaid frame for supporting the same and setting the minimum height of thecutter unit above the ground while permitting raising of the same;spring means interconnecting said frame with said mower deck forresiliently urging said deck in an upward direction to at leastpartially ofi'set the weight of said mower unit; said cutter unitfurther including a plurality of rotatable cutter blades mounted forrotation about the vertical axes and wherein each of said rotatablecutter mountings include a first plate above said cutter deck top plate,a second plate above said cutter deck top plate, a first bearing in saidsecond plate, an inverted conical-shaped housing secured beneath saidsecond plate and extending downwardly therefrom, a second bearinglocated at the bottom of said conical housing, a shaft attached to oneof said blades and extending vertically through said first and secondbearing plates and rotatably received therein and defining a portionextending above said first plate, and a pulley mounted to said shaftabove said first plate and said top plate of said cutter deck.

8. The combination of claim 7 wherein each of said first and secondplates for said side cutter mountings define slots extending in thedirection of travel of said vehicle and said deck defines a slot forreceiving said cutter shaft whereby said sitter units may be moved totighten theirassociated drive belts as they stretch with wear.

1. In combination, a four-wheel traction vehicle having an engine forpowering said vehicle and characterized by having a relatively lowcenter of gravity and wide wheel base; a rotary mowing unit having acovering deck and a plurality of cutting blades mounted to said deck forrotation about a vertical axis and located beneath said deck; adjustablesuspension means for supporting said deck beneath said vehicle at apredetermined but adjustable height above the ground, said suspensionmeans permitting said mowing unit to be raised when the same encountersa ground obstacle while preventing said unit from being lowered belowsaid predetermined height and including flexible link meansinterconnecting said mower deck and said vehicle for supporting saidmowing unit; lift means carried by said vehicle and coupled to saidflexible link means for raising and lowering said mowing unit to saidpredetermined height; drive means including a belt drive system forcoupling power from said engine to drive said blades; first and secondside linkage means separately interconnecting said deck with saidvehicle for maintaining said deck in parallel relation with a lineextending in the direction of travel of said vehicle while permittingsaid mowing unit to be tilted about said line whereby one side of saidmowing unit may be raised in parallel relation and independent of theother side; a wishbone linkage having a neck pivotally connected withthe vehicle frame and first and second base portions pivotallyinterconnecting with the deck of said mowing unit whereby said mowingunit may be raised and lowered relative to said vehicle while stabilizedagainst rotation about a vertical axis; and counterbalancing linkmechanism interconnecting said deck of said mowing unit with saidvehicle for partially offsetting the weight of said mowing unit.
 2. Theapparatus of claim 1 wherein said first and second side linkage meanseach comprise a scissors linkage including first and second linkspivotally interconnected with each other intermediate their ends, afirst end of said first and second links being pivotally connectedrespectively with said mower deck and said vehicle, the other ends ofsaid first and second links defining slots for receiving first andsecond pins connected respectively to said vehicle and said mower deckspaced apart from said first and second pivotal connections whereby saidslots will ride along their associated pins when said mowing unit israised and lowered relative to said vehicle while maintaining each sideof said unit parallel to a horizontal line in the direction of travel ofsaid vehicle.
 3. The apparatus of claim 1 wherein said mowing unit deckdefines an open side for the passage of cut materials and wherein saidcutter blades are horizontally mounted at least about 4 inches beneaththe top of said deck thereby to provide an enlarged upper cavity betweensaid blades and said deck and communicating with said side opening forpassing substantial amounts of cut material above said blades and outsaid side opening when said combination is cutting at high speeds, saidrotary blades arranged in said mower deck including first and secondside blades and a forwardly disposed center blade, the swaths of saidblades overlapping in the direction of movement of said vehicle, saidblades defining an upward draft for moving cut materials thereabove andinto said Enlarged cavity.
 4. The apparatus of claim 3 wherein theforward end of said mower deck includes first and second, forwardly anddownwardly projecting plates extending from the top of said deck andinclined relative to each other to define a pilot for said mowing unit,and a rearwardly and downwardly projecting rear plate, whereby heavyobjects struck by said rotating blades and deflected by said pilot orrear plate of said deck will be directed downwardly and the cut materialdirected upwardly of said blades and exhausted through said sideopening.
 5. The apparatus of claim 4 further comprising first and secondground-engaging runners attached to the sides of said mower deckrespectively and disposed beneath the same to define a minimum heightfor the cutter blades when said runners slide along the ground.
 6. Theapparatus of claim 5 further comprising rear roller means pivotallyattached centrally of said rear plate of said mower deck and extendingbeneath the same for engaging ground elevations occuring in the centerof said mower deck.
 7. In combination, a traction vehicle having a frameand a pair of front wheels and a pair of rear wheels; a cutter unitincluding a deck beneath said vehicle and between said front and rearwheels; scissors linkage mechanism interconnecting each side of saiddeck with said vehicle frame for permitting raising of either side ofsaid cutter unit independently of the other while preventing tilt ofsaid cutter unit in a fore-and-aft direction, link means interconnectingsaid cutter deck and said frame for permitting raising and lowering ofsaid deck while preventing rotation thereof relative to said frame abouta vertical axis; adjustable flexible link means interconnecting saidcutter deck with said frame for supporting the same and setting theminimum height of the cutter unit above the ground while permittingraising of the same; spring means interconnecting said frame with saidmower deck for resiliently urging said deck in an upward direction to atleast partially offset the weight of said mower unit; said cutter unitfurther including a plurality of rotatable cutter blades mounted forrotation about the vertical axes and wherein each of said rotatablecutter mountings include a first plate above said cutter deck top plate,a second plate above said cutter deck top plate, a first bearing in saidsecond plate, an inverted conical-shaped housing secured beneath saidsecond plate and extending downwardly therefrom, a second bearinglocated at the bottom of said conical housing, a shaft attached to oneof said blades and extending vertically through said first and secondbearing plates and rotatably received therein and defining a portionextending above said first plate, and a pulley mounted to said shaftabove said first plate and said top plate of said cutter deck.
 8. Thecombination of claim 7 wherein each of said first and second plates forsaid side cutter mountings define slots extending in the direction oftravel of said vehicle and said deck defines a slot for receiving saidcutter shaft whereby said sitter units may be moved to tighten theirassociated drive belts as they stretch with wear.